Period-to-voltage converting device

Abstract

A period-to-voltage converting device for producing an output voltage corresponding to the varying period of an input signal. The input signal is applied to a frequency divider and a simple logic circuit to control the charging and discharging of first and second capacitors. A charging circuit responsive to a first timing pulse having a width equal to half a period of an input signal charges the first capacitor to a predetermined voltage. A discharging circuit responsive to a second timing pulse having a width equal to the period of the input signal discharges the first capacitor at a constant rate. Another charging circuit responsive to a third timing pulse having a width equal to half a period of the input signal charges the second capacitor to the same voltage across the first capacitor, this voltage being the output voltage proportional to the period of the input signal.

What is claimed is: 
     
       1. A period-to-voltage converting device for producing an output voltage corresponding to the period of an input signal, and comprising: a frequency divider in which the frequency of an input signal is divided by an integer;   a logic circuit which operates to successively produce a first timing pulse having a pulse width equal to half a period of said input signal, a second timing pulse having a pulse width equal to at least one period of said input signal, and a third timing pulse having a pulse width equal to half a period of said input signal, said logic circuit receiving as inputs said input signal and the output of said frequency divider;   first and second capacitor circuits;   a charging circuit for charging said first capacitor circuit to a predetermined voltage in response to said first timing pulse;   a discharging circuit for subjecting said first capacitor circuit to constant current discharge in response to said second timing pulse; and   a gate circuit for transferring the electric charges in said first capacitor circuit into said second capacitor circuit in response to said third timing pulse to charge said second capacitor to an output voltage corresponding to the period of said input signal.   
     
     
       2. A period-to-voltage converting device as claimed in claim 1, in which said logic circuit comprises: a circuit for producing said first timing pulse by obtaining the logical product of the opposite-phase signal of said input signal and the opposite-phase signal of said frequency divider pulse output;   a circuit for providing said frequency division pulse output as said second timing pulse; and   a circuit for producing said third timing pulse by obtaining the logical product of the opposite-phase signal of said frequency divider pulse output and said input signal.